In winter, people's hands need to be protected from the cold. People often put on a pair of gloves to keep warm. However, the hands often need to be used to do work, and it is inconvenient to take the gloves on and off. Thus, a plurality of heating apparatus are provided to warm the hands. One kind of heating apparatus used widely is powered by electrical energy. However, if electrical energy is continually provided to the heating apparatus, the heating apparatus becomes very hot, which is dangerous. Thus, there is room for improvement in the art.